Yes, there is software (Pwnage Tool) and detailed instructions (iClarified.com) on how to unlock/activate/jailbreak a first gen iPhone. If you follow the really nice, pictured instructions, it is pretty easy to do.
Don't use Ziphone. It permanently damages the iPhone with its Bootloaders and such. If you're upgrading in the 1.x status use iLiberty or Liberty+ or w/e. If you're upgrading to 2.x then use pwnagetool or winpwn. They are a lot safer and allow the phone to be restored back to factory condition if you want the phone to be.
But 2.1 1st Generation iPhone CAN be unlocked using pwnagetool and winpwn, to answer your question.
To clear up. Its a 4gb 3.9Bootloader running v2.1 - ziphone served me well back in the day of my other 1st gen, pwnage gives me the sh*ts.
But as long as i can do it thats good. I just have 'fond' memories of every time new SW came out for the 1st gen i would have to wait ages until the unlock came out (ahhh, the memories😛)
Actually it would be GPRS on my network.
I would hardly use it, it would just be in its box stashed away only to come out when i go over my download limit of 500mb on my 3G.
I really miss my 1st Gen, and i won 4.5grand at the casino so i have some loose cash so i thought i would buy what i miss most - and that is a decent build quality iPhone🙂